Needed because they are popular and you probably won’t get a site if you show up without a reservation or necessary regardless of occupancy rate?

I go the Cape Henlopen State Park in DE a couple of times a year. You may camp there without a reservation, but good luck snaring a site during the height of summer if you don’t have a reservation. I booked my site for this past Easter weekend in January. Nearly all the tent sites were already reserved.

Normalizing poor behavior is not a good thing.